Process of manufacturing lubricating oils



UNITED STATES .PATENT acatar? PROCESS or MANUFACTURING lLunmcn'rnzo oms Application September 23, 1933, Serial No. 231,306

` 4 claims. (Ci. 19o-34) I'lllhis invention relates to processes of manufacturing lubricating oils, and more particularly to a process wherein a solvent, preferably a normally gaseous solvent, is employed during the refining 5 of an oil.

in the reiining of hydrocarbon oils, solvents are frequently employed to improve the quality or the oils. For example, a lubricating oil stock may be eiiectively treated with propane to de- M, sludge and dewax the oil.

l-lowever, many of these solvents including propane are relatively diiicult to recover from an -oil especially when the oil is in an acid condition, without impairing the color of the oil.

M object of our invention, therefore, is to provide a process of effectively recovering propane trom an oil without impairing the color of the oil..

rl. iurther object is to provide an efficient procgu ess of treating a solution of oil, propane and acid, and to recover the solvent, and at the same time neutralize and decolorize the oil in a simple manner, which eliminates a number of the steps heretoiore employed in carrying out the operations.

ad With the foregoing and other objects in view.

the invention comprises the novel method hereinartermore specifically described and shown in the accompanying drawing, which illustrates one iorm of the invention. However, it is to be underau stood that the invention comprehends changes, variations and modications which come within the scope of the claims hereunto appended.

The drawing is a diagrammatical view of a sys, tem adapted for use in carrying out the invention;

ag To illustrate one form of the invention, we will describe a continuous system that may be employed in the treatment of a lubricating oil with a normally gaseous solvent, such as propane, but it will be understood that the invention is not limited m to this specific combination.

l designates a storage tank for the oil to be treated, and 2 indicates a source of liquid propane which may be under a pressure of about 100 to 180 pounds. The oil conductor 3 is provided 4with a pump 4 whichkis operated continuously to force the oil through a heater 5, and then into a mixing line G including a mixing nozzle 1.

8 designates a propane conductor leading from the propane tank 2 to the mixing line 6 and in- 50 cluding a heater 9 and a pump l0 whereby the liquid propane is constantly discharged to said mixing line.

The volume of propane may be about two or three times the volume of oil.

The heaters 5 and 9 enable the oil and propane to enter the mixing line 6 at the desired tempera ature, which may be between 80 F. and 120 li..

After the continuous streams of oil and propane are united in the line 6, they are thoroughly mixed at the nozzle 'I to provide a lpropane solution, which is discharged into a settling chamber li. The asphaltic sludge resulting from the settling in said chamber ll is discharged through a pipe l2 at the bottom of the chamber, while the other constituents of the solution slowly rise to the top- M of said chamber and pass out through a pipe ld connected to a pipe I4 which leads to a second settling chamber l5.

Sulfuric acid from asource of supply lli, is conn stantly pumped through the pipe lt, which in 3, cludes a mixing nozzle l1, and the resultant miieture is discharged into the settling chamber lil. The acid sludge slowly settles to the bottom of said chamber I5, where it is discharged through a pipe I8, while the remaining constituents of the to oil and propane solution constantly pass out ol the top of said chamber l5, through a conductor I9.

The acid-treated solution of propane and oil in the conductor i9 may pass directly to a receiver do 2li, or by closing a valve 22 in the conductor Ill,

` and opening a valve 23 in line 24 the solution may be diverted to a propane dewaxing plant 25, where the pressure is reduced to evaporate propane and thereby chill the stock to a low temperature, such del as 40 F., which permits free removal of the wax by filtration. After separation from the wax, the resultant solution of propane and oil may be discharged from the dewaxing plant through a line 26 connected to the conductor I9 leading to the et; receiver 2l).

It will now be understood that the solution of propane and oil can be very advantageously employed in successive continuous operations wherein the propane is first employed in the chamber Il to remove asphaltic sludge, again employed in the chamber l5 to aid in the acid treatment, and thereafter employed as a refrigerent and diluent for the dewaxing operation in 25. This progresl sive unitary method, using the same propane for 45 the successive operations of desludging and. de- Waxing, eliminates a number of expensive steps ordinarily employed to obtain less satisfactory results.

Furthermore, the propane remaining in the 5o treated oil continues to perform an important function in the operation of. decolorizing the oil, and we will also show just how to eventually distill the propane from the acid-containing oil, without causing objectionable oxidation which would result in the production of dark colored tarry substances in the still.

The acid-treated solution of propane and oil, which may be either dewaxed, or undewaxed, is forced through the line 28 by pump 30 to a high pressure still 29. Before the solution of oil and propane in line 28 is discharged into the still 29, a nely divided earth, such as 200 mesh or finer fullers earth, or other suitable contact clay, is

preferably mixed with the solution. 'Ihis comminuted clay is merely an illustration of a suitable material for neutralizing and decolorizing the oil.

As an illustration of one manner of introducing a nely divided earth into the solution, we have shown a mixing tank 3|, wherein contact clay is mixed with a portion of finished oil, entering the tank 3| through a line 32 which is connected to an oil storage tank 33. 'I'he clay slurry formed in the mixing tank 3| is forced by a pump 34 through a conductor 35 into the solution of oil and propane flowing through the conductor 28.

The resultant mixture of clay, oil and propane passing into the still 29 from the conductor 28 may be heated to a temperature of about 225 F. to 250 F., by means of a steam coil 36. The propane evaporated in the still 29 is discharged through a conductor 31, to a return line 38. The propane in line 38, after being condensed in cooler 39, is returned to the propane storage tank 2. The

pressure on the mixture in still 29 is preferably approximately equal to the vapor pressure in the propane storage tank 2'. However, if desired, a pump may be employed in line 38 to return the propane to the storage tank 2.

The oil and clay mixture containing some propane is discharged from the still 29 through a conductor 40 leading to a flash chamber 4|, where the pressure on the mixture is released to about atmospheric pressure. The valve 42 in the conductor 40 may be regulated to give the desired drop in pressure on the mixture entering the chamber 4|. The'propane vaporized in the chamber 4| is discharged through a pipe 43 and passes through a compressor 44 to the return line 38.

The oil and clay mixture passes from the chamber 4| through a conductor 45 to a stripping chamber 46 where it may be heated to about 325 F. to 350 F., and live steam introduced through pipe 41 into the oil mixture to remove the remaining propane. 'Ihe steam and vaporized propane in the chamber 46 pass through a conductor 48 to a jet condenser 49 where the steam is condensed and discharged through a pipe 50. The propane gas in the jet condenser 49 is discharged through a line 5|, and after passing through a compressor 52 in the line 5| the propane is returned to the storage tank 2 through the return line 38.

The oil and clay in the stripping chamber 46 may be forced by a pump 53 through a line 54 to a heater 55 where it is heated to a high temperature, for example 475 F., to further improve the color of the oil. From the heater 55, the oil passes through a conductor 56 to a filter 51 where the clay is removed from the oil. The oil passes from the filter 51 through a line 58 to the finished oil storagetank 33.

In the foregoing operations, it will be observed that the finely divided earth was added to the acid treated solution of oil and propane before the solution was heated to a high temperature to recover the propane. This is one of the ad- '-/antageous features of our invention. as it permits the propane to be distilled from the oil, even while in an acid condition without impairing the color of the oil. In Ithe absence of the nely divided earth, heating the solution of propane and oil in the acid condition, would result in oxidation of the oil and produce dark colored tarry substances, which would darken the oil and form objectionable deposits on the heating surfaces.

vMoreover, the heating of Ithe mixture of oil, propane, and clay in the still 29, and stripping chamber 46, not only does not materially darken the oil, but increases the decolorizing efficiency of the clay, and in many instances produces an oil having a very satisfactory color without a further heating of the oil and clay mixture. When the linished oil is to be obtained Without an additional heating of the oil, we prefer to recover the propane at a relatively high temperature, such as 350 F. to 375 F., or higher.

When it is desirable to further improve the color of the oil after the recovery of the propane, only a relatively small degree of additional heat will be required in the heater 55, as the oil leaves the stripping chamber 46 at a relatively high temperature.

Our process permits Ithe removal of the propane Without employing the steps of neutralizing the oil before removing the propane, and again treating the oil with acid for the contacting operation.

The propane herein referred to is a normally gaseous hydrocarbon, which in commercial practice is usually mixed with various olther hydrocarbons, and it is to be understood that the term propane, as herein used, extends to such mixtures as Well as equivalent normally gaseous hydrocarbons, such as ethane, cyclopropane, .butane and sobutane.

As a specic example of the lubricating oil stock to be treated, we will refer to a residual petroleum lubricating oil stock having the following properties: A. P. I. gravity 21.7, a flash point of 510 F., Saybold. Universal viscosity of 147 at 210 F., and a cold test yof 48 F. Twenty pounds of a-cid for each barrel of oil may be used in treating an oil of this kind, but, of course, the quantity of acid may be varied as desired.

The ratios of propane to lubricating oil stock mixed at the mixing nozzle may be as high as 8 parts propane to l part oil, even 10 to 1 may be used Ito advantage in some cases, although in mostJ cases we have not used more than 4 parts propane to 1 part oil. The temperature of the mixture at said nozzle may be between 80 F. and 120 F., or higher.

Although it is usually advisable to continuously withdraw the sludge from the settling chambers Il and |5, it may be withdrawn periodically, or intermittently.

The order of the procedure may be varied without departing from the invention. For example, one may desludge, or deasphaltize, with a propane solution having four or more parts of propane to one part oil, then remove the wax, and thereafter subject the oil in propane solution to the acid treatment. This can be followed by removal of the propane in accordance with our invention.' In each case the propane is employed in different kinds of successive operations, and the propane remaining with the oil is eventually removed without objectionable oxidation of the relined oil.

We claim:

l. The method of preventing oxidation in using propane and acid to rene lubricating oils which comprises dissolving a lubricating oil stock in liquid propane, treating the resultant solution with sulfuric acid and removing the sludge, mixing nely divided neutralizing earth with the solution of acid-oil and propane, distilling the propane from the oil at a temperature low enough to prevent substantial vaporization of theoil but high enough to cause oxidation of acid-containing oil in the presence of propane, said distilling operation being performed in the presence of a quantity of said finely divided earth suflicient to prevent said oxidation in the heated propane solution, thereby preventing the formation of tarry substances during the distillation of the propane, and separating the finely divided earth from the oil.

2. The method of preventing oxidation in using propane and acid to renne lubricating oils which comprises mixing propane and a lubricating oil stock under a pressure high enough to maintain' the propane in a substantially liquid condition, treating the solution with sulfuric acid and removing the sludge' therefrom, mixing contact clay with oil to form a clay slurry, forcing a stream of the clay slurry into the acid-treated solution of oil and liquid propane, distilling propane from the oil at a temperature low enough to prevent substantial vaporization of the oil but high enough to cause oxidation of acid-containing oil in the presence of propane, said distilling operation being performed in the presence of a quantity of said contact clay sufficient to prevent said oxidation 'n the heated propane solution, thereby preventing the formation of tarry substances in the solution during the distillation of the propane, and separating the clay from the oil.

3. In the art of refining lubricating oils, the method of using propane and acid for progressive operations which comprises mixing propane and a lubricating oil stock under a pressure high enough to maintain the propane in a substantially liquid condition, treating the propane solution under pressure with sulfuric acid, removing the acid sludge, mixing contact clay with a relatively small quantity of oil to form a clay slurry, pumping a stream of the clay slurry into the acidcontaining solution of oil and liquid propane under pressure to neutralize and decolorize the 5 oil, distilling propane from the oil at a temperature low enough to prevent substantial vaporization of the oil, but high enough to cause oxida tion of acid-containing oil in the presence of propane, said distilling operation being performed in 10 the presence of a quantity of said contact clay suiiicient-to prevent said oxidation in the heated propane solution, thereby preventing the formation of tarry substances in the refined solution during the distillation of the propane, and iilter- 1,5 ing the clay from the oil.

4. The method of using propane and acid to refine lubricating oils which comprises mixing propane and a lubricating oil stock under a pressure high enough to maintain the propane 20 in a substantially liquid condition, treating the propane solution under pressure with sulfuric acid, removing the acid sludge, mixing contact clay with a relatively small quantity of oil to form a clay slurry, pumping the clay slurry into the vacid-containing solution of oil and liquid propane under pressure to neutralize and decolorize the oil, distilling propane from the-oil at a temperature low enough to prevent substantial vaporization of the oil, but high enough to cause oxidation of acid-containing oil in the presence of propane, said distilling operation being performed in the presence of a quantity of said contact clay sufficient to prevent said oxidation in 35 -the heated propane solution, thereby preventing the formation of tarry substances in the solution during the distillation of the propane, thereafter increasing the temperature of the mixture of oil 'and clay to obtain the desired color in the oil, 40

and filtering the clay from the oil.

` DWIGHT B. MAPES.

EDDIE M. DONS. 

